UAV Navigation in GNSS-Denied Environment Using Radio Beacons and Onboard Sensor Fusion

Positional knowledge is important for any aerial vehicle. The information enables both detailed surveillance and exploration of the surrounding environment. In recent decades, the usage and development of unmanned aerial vehicles (UAVs) has drastically increased in both civilian and military applications. Making them act autonomously is also of great interest, which is a considerable research field of its own. Precise positioning is especially important in this scenario. Currently, global navigation satellite systems (GNSS), e.g. the American global positioning system (GPS), are mostly used to acquire the positional information of UAVs in outdoor environments. However, these satellite-based systems are sensitive to occlusions and jamming. Also, the systems are mostly operated by nations which could be a potential vulnerability. Therefore, backup navigation systems are of great importance now and certainly in the future. In this thesis, an outdoor UAV positioning system utilizing different sensors is proposed. More specifically, we employ radio beacons to measure angle of arrival (AOA) and received signal strength (RSS) from a transmitting UAV. Also, the onboard inertial measurement unit (IMU) and altimeter are used to provide further information of the dynamic behavior for robust estimation. First, a system design for tracking a UAV is proposed utilizing Kalman filters (KFs), where a decoupled tracker separating the orientation, using the IMU only, and position estimation is incorporated. Further, static positioning using nonlinear and linearized estimators are introduced for proper tracking filter initialization. Moreover, we develop a simultaneous localization and mapping (SLAM) framework to handle uncertainties in radio beacon position and orientation. To evaluate the proposed positioning framework, extensive real-world experiments are conducted to analyze maximum measurement range and noise level of measurements of the radio beacons. Further, the system performa
Opponent: William Nordström